(a) Field of the Invention
The present invention relates to a liquid crystal display and more particularly, to a liquid crystal display having an improved response speed and aperture ratio.
(b) Description of the Related Art
Liquid crystal displays (“LCDs”) are one of the most widely used flat panel displays, and an LCD includes a pair of panels provided with field-generating electrodes, such as pixel electrodes and a common electrode, and a liquid crystal (“LC”) layer interposed between the two panels. The LCD displays images by applying voltages to the field-generating electrodes to generate an electric field in the LC layer that determines the orientations of LC molecules therein to adjust polarization of incident light.
An LCD also includes switching elements connected to the respective pixel electrodes and a plurality of signal lines such as gate lines and data lines for controlling the switching elements and thereby applying voltages to the pixel electrodes. The degree of orientation of LC molecules in the LC layer may be varied by applying voltages of various magnitudes to the pixel electrodes. When the LC molecules in a pixel are oriented so that the polarization of incident light is perpendicular to the polarization of a polarizer, that pixel of the LCD will display black; when the LC molecules in a pixel are oriented so that the polarization of incident light is parallel to the polarization of the polarizer, that pixel of the LCD will display white; when the LC molecules are oriented somewhere between a perpendicular and a parallel alignment, the pixel will display a gray. A typical LCD has a plurality of discreet gray levels corresponding to orientations of the LC molecules between the black and white displays.
Among the LCDs, a vertical alignment (“VA”) mode LCD, which aligns LC molecules such that the long axes of the LC molecules are perpendicular to the panels in the absence of an electric field, has become increasingly popular because of its high contrast ratio and wide reference viewing angle. A wide reference viewing angle is defined as a viewing angle that makes the contrast ratio equal to about 1:10 or as a limit angle for inversion in luminance between the gray levels.
The wide viewing angle of the VA mode LCD can be realized by cutouts in the field-generating electrodes and protrusions on the field-generating electrodes. Since the cutouts and protrusions can determine tilt directions of the LC molecules, the tilt directions can be distributed in several directions by using the cutouts and protrusions such that a reference viewing angle is widened.
However, because it is difficult for light to pass through the portion where the cutouts and protrusions are disposed, these may cause a decrease of the aperture ratio of the LCD. To increase the aperture ratio, an interval between the cutouts or the protrusions may be maximized. However, the liquid crystal molecules that are disposed on the central portion of the region between the cutouts or the protrusions are only slightly influenced by the horizontal electric field formed by the cutouts and the protrusions such that the arrangements of the liquid crystal molecules are scattered. Accordingly, a texture or light leakage is generated, and the response time is increased.